FAILED: patch "[PATCH] binder: cache secctx size before release zeroes it" failed to apply to 6.18-stable tree

[email protected]

author maintainer

2026-07-13 13:19 UTC #0 lore raw

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x b34826e55aad3520ec813f1f367c11b24b29dc9f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026071307-outdated-speed-452e@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b34826e55aad3520ec813f1f367c11b24b29dc9f Mon Sep 17 00:00:00 2001
From: Chris Mason <[email protected]>
Date: Wed, 3 Jun 2026 10:44:54 -0700
Subject: [PATCH] binder: cache secctx size before release zeroes it

binder_transaction() bounds the scatter-gather buffer area with sg_buf_end_offset and subtracts the aligned LSM context size because the secctx is written at the tail of that area. The subtraction reads lsmctx.len, but that field has already been cleared by the time the line runs:

security_secid_to_secctx(secid, &lsmctx) /* lsmctx.len set */
lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64)) extra_buffers_size += lsmctx_aligned_size
...
security_release_secctx(&lsmctx) /* memset zeroes len */
...
sg_buf_end_offset = sg_buf_offset + extra_buffers_size
- ALIGN(lsmctx.len, sizeof(u64)) /* ALIGN(0,8) */

security_release_secctx() does memset(cp, 0, sizeof(*cp)), so lsmctx.len reads back as 0 and the subtraction contributes nothing, leaving sg_buf_end_offset too large by the aligned secctx size on every transaction to a txn_security_ctx node.

Each BINDER_TYPE_PTR object then derives buf_left = sg_buf_end_offset - sg_buf_offset as the sole upper bound on its copy, so the inflated end offset lets the copy run into the bytes that already hold the secctx.

The aligned size must therefore be cached before release rather than re-read from the now-cleared field. Fix by caching it in lsmctx_aligned_size at function scope when it is first computed and subtracting lsmctx_aligned_size instead of re-reading lsmctx.len after release. Reuse the same value for the earlier buf_offset computation.

Fixes 6fba89813ccf ("lsm: ensure the correct LSM context releaser")

Cc stable <[email protected]>

Assisted-by kres:claude-opus-4-8

Signed-off-by Chris Mason <[email protected]>

Reviewed-by Alice Ryhl <[email protected]>

Acked-by Carlos Llamas <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

drivers/android/binder.c +6 -6

index ec0ab4f28530..c48c22264266 100644
@@ -3080,6 +3080,7 @@ static void binder_transaction(struct binder_proc *proc,
 	int t_debug_id = atomic_inc_return(&binder_last_id);
 	ktime_t t_start_time = ktime_get();
 	struct lsm_context lsmctx = { };
+	size_t lsmctx_aligned_size = 0;
 	LIST_HEAD(sgc_head);
 	LIST_HEAD(pf_head);
 	const void __user *user_buffer = (const void __user *)

@@ -3346,7 +3347,6 @@ static void binder_transaction(struct binder_proc *proc,
 
 	if (target_node && target_node->txn_security_ctx) {
 		u32 secid;
-		size_t added_size;
 
 		security_cred_getsecid(proc->cred, &secid);
 		ret = security_secid_to_secctx(secid, &lsmctx);

@@ -3358,9 +3358,9 @@ static void binder_transaction(struct binder_proc *proc,
 			return_error_line = __LINE__;
 			goto err_get_secctx_failed;
 		}
-		added_size = ALIGN(lsmctx.len, sizeof(u64));
-		extra_buffers_size += added_size;
-		if (extra_buffers_size < added_size) {
+		lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64));
+		extra_buffers_size += lsmctx_aligned_size;
+		if (extra_buffers_size < lsmctx_aligned_size) {
 			binder_txn_error("%d:%d integer overflow of extra_buffers_size\n",
 				thread->pid, proc->pid);
 			return_error = BR_FAILED_REPLY;

@@ -3397,7 +3397,7 @@ static void binder_transaction(struct binder_proc *proc,
 		size_t buf_offset = ALIGN(tr->data_size, sizeof(void *)) +
 				    ALIGN(tr->offsets_size, sizeof(void *)) +
 				    ALIGN(extra_buffers_size, sizeof(void *)) -
-				    ALIGN(lsmctx.len, sizeof(u64));
+				    lsmctx_aligned_size;
 
 		t->security_ctx = t->buffer->user_data + buf_offset;
 		err = binder_alloc_copy_to_buffer(&target_proc->alloc,

@@ -3452,7 +3452,7 @@ static void binder_transaction(struct binder_proc *proc,
 	off_end_offset = off_start_offset + tr->offsets_size;
 	sg_buf_offset = ALIGN(off_end_offset, sizeof(void *));
 	sg_buf_end_offset = sg_buf_offset + extra_buffers_size -
-		ALIGN(lsmctx.len, sizeof(u64));
+		lsmctx_aligned_size;
 	off_min = 0;
 	for (buffer_offset = off_start_offset; buffer_offset < off_end_offset;
 	     buffer_offset += sizeof(binder_size_t)) {

Sasha Levin

maintainer

2026-07-14 13:43 UTC #1 lore raw

PATCH 1/2 binder: Use LIST_HEAD() to initialize on stack list head

From: Jisheng Zhang <[email protected]>

[ Upstream commit 91f818b184b44b105b1c92859ea8d2d6f47912a9 ]

Use LIST_HEAD to initialize on stack list head. No intentional functional impact.

Change generated with below coccinelle script:

@@
identifier name;
@@
- struct list_head name;
+ LIST_HEAD(name);
... when != name
- INIT_LIST_HEAD(&name);

Signed-off-by Jisheng Zhang <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

Stable-dep-of: b34826e55aad ("binder: cache secctx size before release zeroes it")

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/android/binder.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

drivers/android/binder.c +2 -4

index a6b3bfe0d9b81f..81ebc5762fb422 100644
@@ -3080,12 +3080,10 @@ static void binder_transaction(struct binder_proc *proc,
 	int t_debug_id = atomic_inc_return(&binder_last_id);
 	ktime_t t_start_time = ktime_get();
 	struct lsm_context lsmctx = { };
-	struct list_head sgc_head;
-	struct list_head pf_head;
+	LIST_HEAD(sgc_head);
+	LIST_HEAD(pf_head);
 	const void __user *user_buffer = (const void __user *)
 				(uintptr_t)tr->data.ptr.buffer;
-	INIT_LIST_HEAD(&sgc_head);
-	INIT_LIST_HEAD(&pf_head);
 
 	e = binder_transaction_log_add(&binder_transaction_log);
 	e->debug_id = t_debug_id;

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-07-14 13:43 UTC #2 lore raw

PATCH 2/2 binder: cache secctx size before release zeroes it

From: Chris Mason <[email protected]>

[ Upstream commit b34826e55aad3520ec813f1f367c11b24b29dc9f ]

binder_transaction() bounds the scatter-gather buffer area with sg_buf_end_offset and subtracts the aligned LSM context size because the secctx is written at the tail of that area. The subtraction reads lsmctx.len, but that field has already been cleared by the time the line runs:

security_secid_to_secctx(secid, &lsmctx) /* lsmctx.len set */
lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64)) extra_buffers_size += lsmctx_aligned_size
...
security_release_secctx(&lsmctx) /* memset zeroes len */
...
sg_buf_end_offset = sg_buf_offset + extra_buffers_size
- ALIGN(lsmctx.len, sizeof(u64)) /* ALIGN(0,8) */

security_release_secctx() does memset(cp, 0, sizeof(*cp)), so lsmctx.len reads back as 0 and the subtraction contributes nothing, leaving sg_buf_end_offset too large by the aligned secctx size on every transaction to a txn_security_ctx node.

Each BINDER_TYPE_PTR object then derives buf_left = sg_buf_end_offset - sg_buf_offset as the sole upper bound on its copy, so the inflated end offset lets the copy run into the bytes that already hold the secctx.

The aligned size must therefore be cached before release rather than re-read from the now-cleared field. Fix by caching it in lsmctx_aligned_size at function scope when it is first computed and subtracting lsmctx_aligned_size instead of re-reading lsmctx.len after release. Reuse the same value for the earlier buf_offset computation.

Fixes 6fba89813ccf ("lsm: ensure the correct LSM context releaser")

Cc stable <[email protected]>

Assisted-by kres:claude-opus-4-8

Signed-off-by Chris Mason <[email protected]>

Reviewed-by Alice Ryhl <[email protected]>

Acked-by Carlos Llamas <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Greg Kroah-Hartman <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/android/binder.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

drivers/android/binder.c +6 -6

index 81ebc5762fb422..abfad4df2938bb 100644
@@ -3080,6 +3080,7 @@ static void binder_transaction(struct binder_proc *proc,
 	int t_debug_id = atomic_inc_return(&binder_last_id);
 	ktime_t t_start_time = ktime_get();
 	struct lsm_context lsmctx = { };
+	size_t lsmctx_aligned_size = 0;
 	LIST_HEAD(sgc_head);
 	LIST_HEAD(pf_head);
 	const void __user *user_buffer = (const void __user *)

@@ -3346,7 +3347,6 @@ static void binder_transaction(struct binder_proc *proc,
 
 	if (target_node && target_node->txn_security_ctx) {
 		u32 secid;
-		size_t added_size;
 
 		security_cred_getsecid(proc->cred, &secid);
 		ret = security_secid_to_secctx(secid, &lsmctx);

@@ -3358,9 +3358,9 @@ static void binder_transaction(struct binder_proc *proc,
 			return_error_line = __LINE__;
 			goto err_get_secctx_failed;
 		}
-		added_size = ALIGN(lsmctx.len, sizeof(u64));
-		extra_buffers_size += added_size;
-		if (extra_buffers_size < added_size) {
+		lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64));
+		extra_buffers_size += lsmctx_aligned_size;
+		if (extra_buffers_size < lsmctx_aligned_size) {
 			binder_txn_error("%d:%d integer overflow of extra_buffers_size\n",
 				thread->pid, proc->pid);
 			return_error = BR_FAILED_REPLY;

@@ -3397,7 +3397,7 @@ static void binder_transaction(struct binder_proc *proc,
 		size_t buf_offset = ALIGN(tr->data_size, sizeof(void *)) +
 				    ALIGN(tr->offsets_size, sizeof(void *)) +
 				    ALIGN(extra_buffers_size, sizeof(void *)) -
-				    ALIGN(lsmctx.len, sizeof(u64));
+				    lsmctx_aligned_size;
 
 		t->security_ctx = t->buffer->user_data + buf_offset;
 		err = binder_alloc_copy_to_buffer(&target_proc->alloc,

@@ -3452,7 +3452,7 @@ static void binder_transaction(struct binder_proc *proc,
 	off_end_offset = off_start_offset + tr->offsets_size;
 	sg_buf_offset = ALIGN(off_end_offset, sizeof(void *));
 	sg_buf_end_offset = sg_buf_offset + extra_buffers_size -
-		ALIGN(lsmctx.len, sizeof(u64));
+		lsmctx_aligned_size;
 	off_min = 0;
 	for (buffer_offset = off_start_offset; buffer_offset < off_end_offset;
 	     buffer_offset += sizeof(binder_size_t)) {

Signature · 1 line

2.53.0